About MAC Addresses

KALM-150x150"Tom provides a brief explanation of what MAC addresses are and why your Windows computer, and all your wireless devices, has one.

Featuring Tom Merritt.

MP3

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Episode Script
This says you need a MAC address

But you have a PC

Wait that’s not what that means?

Are you confused?

Don’t be.

Let’s help you Know a Little more about MAC Addresses

A MAC address has nothing to do with a Macintosh Computer. It’s kind of an “all men are Socrates” thing. “All Macs have Mac Addresses, not all MAC addresses are in Macs.”
The MAC address is used by Ethernet, WiFI and Bluetooth to keep straight which device is which. A lot of router management software lets you see what devices are connected to your network and the way they do it is the MAC address. That’s those weird numbers and letters with colons separating them.
The MAC in MAC address stands for Media Access Control.
Which has nothing to do with the news media.
The MAC address is a unique number assigned to the Network Interface Controller or NIC, in your device. Your network card.
So it’s a number used to identify your computer or your phone or other device to the network.
Some people get confused between this and an IP address. We won’t be getting into what an IP address is, but the simple version is that an IP address is assigned by your internet provider and can change. The MAC address is assigned to your device. And it generally only changes if you swap out the network card.
The MAC address is used by Ethernet, WiFI and Bluetooth to keep straight which device is which. A lot of router management software lets you see what devices are connected to your network and the way they do it is the MAC address. That’s those weird numbers and letters with colons separating them.
So how does the MAC address get assigned to a device?
They’re almost always assigned by the device manufacturer.
The MAC address itself is usually a 48-bit number represented as six groups of two hexadecimal digits often separated by colons or sometimes hyphens. Hexadecimal means after 9 you get letters. A-f. That’s why mac address are sometimes 85:6f etc.
The Institute of Electrical and Electronics Engineers aka the IEEE manages allocation of MAC Addresses and also manages a 64-bit address space for non-Ethernet applications.
The first part of a MAC address usually contains an Organizationally Unique Identifier or OUI. OUIs are 24-bit numbers purchased from the IEEE. So those first three pairs of numbers and letters are the OUI. They tell you who made the device.
The rest of the address is assigned by that organization however they want. The only rule is they can’t assign the same number to more than one device.
This version of the Mac address is often called the hardware address, the Ethernet hardware address or the burned-in address. It’s meant to be permanent.
It ends up being something like 00:14:22:9f:86:61
In that example you know it’s a Dell because the OUI 00:14:22 is assigned to Dell equipment.
These burned-in addresses, assigned by manufacturers are considered a Universally Administered Address.
There is something called a Locally Administered Address which can be assigned by a network administrator and override the “burned-in” address.
For most people on home networks your MAC address is the one that came with your machine.
You want it to always be the same. It’s good for network diagnosis. And it allows other things like filtering network access by MAC address, so that only the devices you want to connect to a network can.
Also keep in mind that one device, like your laptop, may have more than one MAC address. The MAC address is tied to the network interface card. If you have an Ethernet adapter and a wireless adapter, those will each have their own MAC addresses even though they’re in the same machine.
NOW. Most of the time MAC addresses don’t change. BUT some network interfaces support changing their MAC address. Also, Some utilities permit randomizing the MAC address at the time of booting to prevent tracking. So they’re the same until you reboot. And Android, Linux, Windows and iOS randomize the assignment of a MAC address when scanning for wireless access points so the access points, the WiFi you’re connecting to, doesn’t see your true MAC address. This prevents tracking.You’re not connecting to the vast majority of the WiFi access points your phone scans, so why leave a trail?
OK so how do you find your MAC address?
You’ll probably want to look in your Operating System. Some devices print them on the box… but where’s the box again? They also might be on a very tiny label on the machine. Which means you need your glasses. So OS is your best bet.
In Windows you can find it by running ipconfig, in Linux you run fconfig in a Macintosh its in the Advanced network section of system preferences. In iOS it’s in the About section of general under settings and in Android it’s in status under “about device” in Settings.
I hope this helps you know the difference between a Mac and a MAC address, the difference between an IP address and a MAC address and helps you understand all those weird numbers and letters separated by colons you see sometimes.
In other words I hope now you know a little more about MAC addresses.